This invention relates to an ultra miniature pressure sensor and guide wire and apparatus using the same and method, which is particularly suitable for making pressure measurements in coronary arteries of human beings.
It has been well known that it is desirable to make pressure measurements in vessels and particularly in coronary arteries with the advent of angioplasty. Typically in the past, such pressure measurements have been made by measuring the pressure at a proximal extremity of a lumen provided in a catheter advanced into the coronary artery of interest. However, such an approach has been less efficacious as the diameters of the catheters became smaller with the need to advance the catheter into smaller vessels. This made necessary the use of smaller lumens which gave less accurate pressure measurements and in the smallest catheters necessitated the elimination of such a pressure lumen entirely. In an attempt to overcome these difficulties, ultra miniature pressure sensors have been proposed for use on the distal extremities of catheters. However, it has not been feasible prior to the present invention to provide such ultra miniature pressure sensors which are capable of being incorporated in a guide wire for making pressure measurements in a very small arterial vessels. There is therefore a need for a new and improved ultra miniature pressure sensor and a guide wire and apparatus utilizing the same.
In general it is an object of the present invention to provide an ultra miniature pressure sensor and guide wire and apparatus utilizing the same making possible pressure and velocity measurements.
Another object of the invention is to provide a sensor which can be utilized on the distal extremity of a guide wire 0.018xe2x80x3 or 0.014xe2x80x3 in diameter.
Another object of the invention is to provide a sensor of the above character which is formed of a silicon chip of a small dimension which is reinforced by an additional member to provide reinforcement for the chip.
Another object of the invention is to provide a sensor of the above character in which a thin diaphragm is formed in the crystalline silicon chip.
Another object of the invention is to provide a sensor of the above character in which the reinforcing member extends for approximately 200 microns beyond the silicon diaphragm.
Another object of the invention is to provide a guide wire with the above character in which the number of conducting wires required is kept to a minimum.
Another object of the invention is to provide a guide wire and method in which simultaneous pressure and velocity measurements can be made.
Another object of the invention is to provide a guide wire of the above character in which the diaphragm area has been maximized.
Another object of the invention is to provide a guide wire with the above character in which two pressure sensors are provided on the guide wire which are spaced apart so that pressure measurements can be made on both sides of a stenosis.
Another object of the invention is to provide a guide wire of the above character in which the sensors are covered to prevent the formation of blood clots.
Another object of the invention is to provide an apparatus of the above character which includes a guide wire with an integral inflatable balloon.
Another object of the invention is to provide an apparatus of the above character in which temperature compensation can be provided.
Another object of the invention is to provide an apparatus of the above character which can be utilized in a half-bridge configuration.